Broad [OIII] in the globular cluster RZ 2109: X-ray ionized nova ejecta?

TL;DR

This paper proposes that the broad [OIII] emission in globular cluster RZ 2109 results from nova ejecta photoionized by a nearby X-ray source, explaining spectral features and predicting observable evolution.

Contribution

It introduces a plausible model where nova ejecta are ionized by X-ray emission, accounting for observed spectral properties and providing testable predictions.

Findings

Nova ejecta can produce broad [OIII] emission when photoionized by X-ray sources.

The scenario explains spectral features like line luminosity and asymmetry.

Predicted evolution of line emission can be tested with future observations.

Abstract

We study the possibility that the very broad (~1500 km/s) and luminous (L_5007 ~ 1.4e37 erg/s) [OIII] line emission observed in the globular cluster RZ 2109 might be explained with the photoionization of nova ejecta by the bright (L_X ~ 4e39 erg/s) X-ray source hosted in the same globular cluster. We find that such scenario is plausible and explains most of the features of the RZ 2109 spectrum (line luminosity, absence of H emission lines, peculiar asymmetry of the line profile); on the other hand, it requires the nova ejecta to be relatively massive (>~ 0.5e-3 Msun}), and the nova to be located at a distance <~ 0.1 pc from the X-ray source. We also predict the time evolution of the RZ 2109 line emission, so that future observations can be used to test this scenario.